This invention relates to fuel injection control for starting up an internal combustion engine.
Tokkai 2000-45841 published by the Japanese Patent Office in 2000 discloses simultaneous fuel injection to all cylinders of an engine immediately after the ignition switch is switched to the ON position.
In a spark-ignition engine injecting fuel sequentially into the intake port, fuel injected during cranking of the engine adheres to the wall surface of the intake port and tends to form a flow along the wall. This phenomenon is hereafter referred to as xe2x80x9cwall flowxe2x80x9d. Consequently time is required for fuel to reach the combustion chamber and preferred stability of combustion during cranking of the engine cannot be obtained. The prior-art technique aims to form a wall flow in advance as a result of injecting fuel all at once to all cylinders immediately after the ignition switch is turned to the ON position. As a result, fuel injected sequentially to respective cylinders thereafter flows into the combustion chamber smoothly without adhering to the wall face of the intake port.
Spark ignition of the air-fuel mixture in each cylinder is generally performed in the vicinity of the compression dead center. However, it is noted that each cylinder performs respectively different strokes when simultaneous injection to all cylinders is performed. Furthermore in the period after simultaneous injection to all cylinders until initial spark ignition to each cylinder, some cylinders undergo sequential fuel injection while others do not undergo sequential fuel injection.
As a result, a deviation is produced in the air-fuel ratio of the fuel mixture at initial sparking ignition in each cylinder. In cylinders having a lean air-fuel ratio, misfiring may result. In cylinders having a rich air-fuel ratio, incomplete combustion may result. Both misfiring or incomplete combustion have an adverse effect on the stability of the engine and on the exhaust emission components.
It is therefore an object of this invention to increase stability of combustion in each cylinder when starting an engine which performs sequential fuel injection.
In order to achieve above object, this invention provides a fuel injection control device for an internal combustion engine, the engine comprising a crankshaft, a plurality of cylinders which sequentially perform a combustion of fuel and a starter motor which cranks up the engine, each of the cylinders having an intake port and a fuel injector which injects fuel into the intake port and sequentially performing an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke.
The device further comprises a first sensor which identifies a cylinder in a specific position in a specific stroke and generates a corresponding signal; a second sensor which detects an engine temperature; and a controller.
The controller functions to determine whether or not the engine temperature is higher than a first predetermined temperature; execute a cylinder-stroke identification identifying a present stroke of each cylinder based on the signal generated by the first sensor; command the fuel injectors to simultaneously perform a primary fuel injection for a cylinder in the exhaust stroke and for a cylinder in the intake stroke, on a first execution of the cylinder-stroke identification, if the engine temperature is higher than the first predetermined temperature; and command the fuel injectors to perform the primary fuel injection only for a cylinder in the intake stroke, on the first execution of the cylinder-stroke identification, if the engine temperature is less than the first predetermined temperature.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.